/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.transforms.windowing;



import com.bff.gaia.unified.sdk.coders.*;

import com.bff.gaia.unified.sdk.coders.Coder;

import com.bff.gaia.unified.sdk.coders.CoderException;

import com.bff.gaia.unified.sdk.coders.DurationCoder;

import com.bff.gaia.unified.sdk.coders.InstantCoder;

import com.bff.gaia.unified.sdk.coders.StructuredCoder;

import org.joda.time.Duration;

import org.joda.time.Instant;

import org.joda.time.ReadableDuration;



import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.util.Collections;

import java.util.List;



/**

 * An implementation of {@link BoundedWindow} that represents an interval from {@link #start}

 * (inclusive) to {@link #end} (exclusive).

 */

public class IntervalWindow extends BoundedWindow implements Comparable<IntervalWindow> {

  /** Start of the interval, inclusive. */

  private final Instant start;



  /** End of the interval, exclusive. */

  private final Instant end;



  /** Creates a new IntervalWindow that represents the half-open time interval [start, end). */

  public IntervalWindow(Instant start, Instant end) {

    this.start = start;

    this.end = end;

  }



  public IntervalWindow(Instant start, ReadableDuration size) {

    this.start = start;

    this.end = start.plus(size);

  }



  /** Returns the start of this window, inclusive. */

  public Instant start() {

    return start;

  }



  /** Returns the end of this window, exclusive. */

  public Instant end() {

    return end;

  }



  /** Returns the largest timestamp that can be included in this window. */

  @Override

  public Instant maxTimestamp() {

    // end not inclusive

    return end.minus(1);

  }



  /** Returns whether this window contains the given window. */

  public boolean contains(IntervalWindow other) {

    return !this.start.isAfter(other.start) && !this.end.isBefore(other.end);

  }



  /** Returns whether this window is disjoint from the given window. */

  public boolean isDisjoint(IntervalWindow other) {

    return !this.end.isAfter(other.start) || !other.end.isAfter(this.start);

  }



  /** Returns whether this window intersects the given window. */

  public boolean intersects(IntervalWindow other) {

    return !isDisjoint(other);

  }



  /** Returns the minimal window that includes both this window and the given window. */

  public IntervalWindow span(IntervalWindow other) {

    return new IntervalWindow(

        new Instant(Math.min(start.getMillis(), other.start.getMillis())),

        new Instant(Math.max(end.getMillis(), other.end.getMillis())));

  }



  @Override

  public boolean equals(Object o) {

    return (o instanceof IntervalWindow)

        && ((IntervalWindow) o).end.isEqual(end)

        && ((IntervalWindow) o).start.isEqual(start);

  }



  @Override

  public int hashCode() {

    // The end values are themselves likely to be arithmetic sequence, which

    // is a poor distribution to use for a hashtable, so we

    // add a highly non-linear transformation.

    return (int) (start.getMillis() + modInverse((int) (end.getMillis() << 1) + 1));

  }



  /** Compute the inverse of (odd) x mod 2^32. */

  private int modInverse(int x) {

    // Cube gives inverse mod 2^4, as x^4 == 1 (mod 2^4) for all odd x.

    int inverse = x * x * x;

    // Newton iteration doubles correct bits at each step.

    inverse *= 2 - x * inverse;

    inverse *= 2 - x * inverse;

    inverse *= 2 - x * inverse;

    return inverse;

  }



  @Override

  public String toString() {

    return "[" + start + ".." + end + ")";

  }



  @Override

  public int compareTo(IntervalWindow o) {

    if (start.isEqual(o.start)) {

      return end.compareTo(o.end);

    }

    return start.compareTo(o.start);

  }



  /** Returns a {@link Coder} suitable for {@link IntervalWindow}. */

  public static Coder<IntervalWindow> getCoder() {

    return IntervalWindowCoder.of();

  }



  /** Encodes an {@link IntervalWindow} as a pair of its upper bound and duration. */

  public static class IntervalWindowCoder extends StructuredCoder<IntervalWindow> {



    private static final IntervalWindowCoder INSTANCE = new IntervalWindowCoder();



    private static final Coder<Instant> instantCoder = InstantCoder.of();

    private static final Coder<ReadableDuration> durationCoder = DurationCoder.of();



    public static IntervalWindowCoder of() {

      return INSTANCE;

    }



    @Override

    public void encode(IntervalWindow window, OutputStream outStream)

        throws IOException, CoderException {

      instantCoder.encode(window.end, outStream);

      durationCoder.encode(new Duration(window.start, window.end), outStream);

    }



    @Override

    public IntervalWindow decode(InputStream inStream) throws IOException, CoderException {

      Instant end = instantCoder.decode(inStream);

      ReadableDuration duration = durationCoder.decode(inStream);

      return new IntervalWindow(end.minus(duration), end);

    }



    @Override

    public void verifyDeterministic() throws NonDeterministicException {

      instantCoder.verifyDeterministic();

      durationCoder.verifyDeterministic();

    }



    @Override

    public boolean consistentWithEquals() {

      return instantCoder.consistentWithEquals() && durationCoder.consistentWithEquals();

    }



    @Override

    public List<? extends Coder<?>> getCoderArguments() {

      return Collections.emptyList();

    }

  }

}